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Xanthogranulomatous pyelonephritis

Case contributed by Dalia Ibrahim
Diagnosis almost certain

Presentation

Left loin pain and dysuria. History of left renal stones.

Patient Data

Age: 40 years
Gender: Female

Enlarged left kidney showing lost renal outline and large staghorn stones within the middle and lower calyces. Dilated renal calyces give a multiloculated appearance (bear paw sign) with the contracted renal pelvis. Smudging of the perinephric fat planes.

The left ureter is dilated secondary to the lower ureteric stone. The left ureter also shows diffuse mural thickening and periureteric smudging.

Urine culture and sensitivity revealed Proteus SPP infection.

Case Discussion

Xanthogranulomatous pyelonephritis (XGP) is a rare form of chronic pyelonephritis and represents a chronic granulomatous disease resulting in a non-functioning kidney.

Radiological features include an enlarged kidney with a lost renal outline, associated with large stage horn stone, contracted renal pelvis, and dilated renal calyces giving the (Bear paw sign). Sometimes there is a perinephric extension with thickening of Gerota's fascia. 

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